Question: Who is {head of government} of {Düsseldorf} whose {start time} is {1820-7-19} ?
Paraphrase: Who was the head of government of Dusseldorf in 1820?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q1718 p:P6 ?s . ?s ps:P6 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1820')) }